Alcohols and organic chemicals with hydroxyl and carbonyl functional groups are important to industrial processes and the production of light alcohol fuels. At present, several different processes are used for production of alcohols. Most alcohols are produced from oil or natural gas, while some including ethanol and pentanol are produced biologically. Hydroxyl groups are often introduced to organic molecules via catalytic hydrogenation of aldehydes or acid catalyzed hydration of alkenes. Some specific examples include methanol, which is produced by catalytic conversion of synthesis gas at high temperature and pressure. Ethanol is produced by acid catalyzed hydration of ethylene or by various microorganisms via fermentation of sugars.
Two major processes exist for propanol production. Acid catalyzed hydration of propylene is performed, resulting in a mixture of both isopropanol and n-propanol. Another process to make n-propanol is hydroformylation of ethylene to propionaldehyde followed by catalytic hydrogenation of propionaldehyde to n-propanol. N-butanol is produced in a manner similar to that of n-propanol. Propylene is converted to butyraldehyde via hydroformylation. The butyraldehyde is then catalytically hydrogenated to n-butanol. Sec-butanol is produced in a manner similar to ethanol, by the acid catalyzed hydration of 1-butene or 2-butene. Isomers of pentanol are primarily produced by the distillation of fusel oil. Fusel oil is a product of some biological fermentation processes. Hexanol and higher order alcohols are commonly produced by oligomerization of ethylene, which results in a mix of different products separated via distillation.
At present, many different techniques are currently used to create other organic products. Biological processes, such as fermentation of sugars, produce ethanol or fusel oil. The Fischer-Tropsch process is used for conversion of synthesis gases to organic molecules. Hydroformylation of alkenes is followed by catalytic hydrogenation to alcohols or alkanes. Polymerization of alkenes results in organic products. Electrochemical hydrodimerization of alkenes, notably the Monsanto process, produces adiponitrile.
Existing electrochemical and photochemical processes/systems have one or more of the following problems that prevent commercialization on a large scale. Selectively producing some alcohols, notably isopropanol, butanol, pentanol, and higher order alcohols is difficult. Selectively reducing carboxyl or carbonyl groups is also difficult without undesirable side reactions such as hydrogenation of aromatic molecules or heterocycles. Many existing processes, notably the Fischer-Tropsch process, make multiple products that are subsequently separated. Production of some aldehydes and alcohols use multi-step reactions that collectively have low energy efficiency. Likewise, hydrodimerization without a catalyst can be very inefficient. Existing reaction pathways use high heat, high temperature and/or highly acid environments. The heat conditions result in the use of expensive materials for the reactors. Many existing processes, both thermally and electrochemically driven, also use alkenes as a starting material.